Synthetic fiber filled erosion control blanket

ABSTRACT

A durable erosion control blanket featuring a novel synthetic fiber filler is disclosed. The erosion control blanket of the present invention addresses the need for a particularly resilient erosion control blanket through the use of a post-consumer, crimped, polyester fiber filler material. In one embodiment, the post-consumer fiber material is of polyethylene terephthalate (PET) readily available in post-consumer form from the recycling of soda bottles. In short, a preferred filler material for the blanket of the present invention would utilize recycled soda bottle material which has been converted into a crimped, highly-resilient fibrous filler. It is, thus, possible to achieve the desired physical and mechanical properties in the erosion control blanket of the present invention while conserving natural resources to some extent by using a readily available post-consumer polymer material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 09/648,906 filed Aug. 25, 2000, now U.S. Pat. No. 6,855,650.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to erosion control blankets and, moreparticularly, to a soil erosion control blanket having a synthetic,fibrous filler material which is substantially non-biodegradable. Theerosion control blanket of the present invention is designed to preventsoil erosion and runoff, as well as permitting the in-growth of grassesand other vegetation, while retaining a near original state and notdegrading significantly over a number of years.

2. History of the Related Art

Erosion control blankets have established commercial acceptance and useworldwide. Erosion control blankets are articles which resemble a formof fibrous matting in which two outer layers of netting or othermaterial are commonly used to form an envelope or covering about afibrous interior filler layer. These blankets are commonly used toreduce soil erosion and runoff from erosion-prone areas such as highwayembankments or water drainage ditches.

Several different styles of erosion control blankets or mats arecommonly in use today. One particular style of blanket that does not usea netting material is set forth and shown in U.S. Pat. No. 5,786,281which is assigned to the assignee of the present invention andincorporated herein by reference. Other styles may include at least twoouter netting or facing layers that are filled with a loose fibrousmaterial. For example, one particularly effective erosion controlblanket is the CURLEX or excelsior fiber blanket manufactured and soldby the American Excelsior Company of Arlington, Tex. since 1964. Thisblanket is fabricated in elongated rectangular mat form, from elongated,randomly intertwined wood fibers commonly referred to as excelsior.Prior art erosion control blankets and mats such as these are commonlyused in conjunction with commercial or residential construction projectsin an attempt to control soil loss and runoff into adjoining areas. Theblankets are unrolled along the earth area to be protected againsterosion, and are secured along the sides of one another and to theunderlying ground area with a series of conventional ground staplemembers. The ground staple members may be made of steel, wood, plasticor other materials and serve to anchor the mats securely to the coveredearth area. Additionally, in some applications, erosion control blanketsor mats such as these may be rolled to form a sort of artificial curb orbarrier at the edge of a property or construction site.

The netting and loose fiber filler construction permits blankets or matsof this kind to be fairly light in weight and also to permit theingrowth of grasses and other vegetation into and through the blanket.The netting primarily serves to hold the loose fiber filler togetherwhile providing a large number of openings for plant ingrowth. As theseblankets will frequently become a fixture in their installment site, itis often desirable to form the inner fibrous layer of the blanket ofvarious types of biodegradable materials. By way of example, recycledpaper or fiberized waste paper, wood fibers or excelsior, straw or othernaturally fibrous materials such as coconut husks may be used to providea biodegradable filler material. However, in some erosion-prone areassuch as water runoff ditches and the like, it is particularly useful tohave an erosion control blanket or mat with a more substantial andpermanent filling which will not significantly degrade over long periodsof time.

One solution to the problem referenced above is the use of polymeric orother synthetic fibers as filler materials. Some synthetic fillermaterials which have been suggested include polyethylene, polypropyleneor nylon fibers and blends of fibers such as these with organic orbiodegradable fibers such as those noted above. Several shortcomingshave been noted by end users with these blankets which include syntheticfibers in that the blankets tend to become matted down or thinner overtime and tend to lose their loft or three-dimensionality. As blanketsbecome matted down, the fibers in the filler tend to become more tightlypacked, and the subsequent in-growth of grasses and other vegetationbecomes increasingly difficult. Prior art attempts to resolve fibermatting problems have involved the use of multiple netting layersdisposed throughout the filler material and netting which is corrugatedor shaped to hold a more three-dimensional structure. However, thesesolutions may involve significant additional material and labor costs toproduce an erosion control blanket. Moreover, synthetic/organic blendedfillers tend to degrade over time much like organic-only fillers, andmerely do so at a slower rate. Thus, while synthetic-only fillers forerosion control blankets have been suggested, these appear to besomewhat wasteful of natural resources and still suffer fromshortcomings in the areas of fiber resiliency and loft.

SUMMARY OF THE INVENTION

The present invention overcomes the shortcoming of the existing designsand satisfies a significant need for a durable erosion control blanketwith improved loft and resiliency properties. More specifically, theerosion control blanket of the present invention addresses the need foran erosion control blanket which does not significantly degrade over anumber of years and maintains a high degree of resiliency or loft whenin use. In one embodiment of the present invention, the erosion controlblanket has at least three layers including a top sheet, a fillermaterial and a bottom sheet. The top and bottom sheets generallyresemble an open-mesh material or netting. Many of the particularphysical characteristics of the erosion control blanket are achievedthrough the use of a novel synthetic fiber filler material. The fillermaterial for use in the erosion control blanket is a made up of aplurality of crimped polymer fibers which form a three-dimensionalmatrix between the top sheet and the bottom sheet. Moreover, it ispossible to form the crimped polymer fibers from post-consumer polyesterfiber material such as polyethylene terephthalate (PET). Although it isto be understood that the synthetic filler is not limited to thisparticular material, PET is desirable in that it is commonly used tomake soda bottles and other translucent packaging containers, and isconsequently readily available in post-consumer form. Thus, it ispossible to achieve the desired physical and mechanical properties inthe erosion control blanket of the present invention while conservingnatural resources to some extent by using a readily availablepost-consumer polymer material.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the erosion control blanket accordingto the present invention may be obtained by reference to the followingdetailed description when taken in conjunction with the accompanyingdrawings wherein:

FIG. 1 is a top plan view of a section of an erosion control blanketconstructed in accordance with the present invention;

FIG. 2 is a cut-away side view of a section of an erosion controlblanket constructed in accordance with the present invention;

FIG. 3 is a top perspective view of a section of an erosion controlblanket constructed in accordance with the present invention; and

FIG. 4 is a block diagram of steps which are carried out to produce anerosion control blanket constructed in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings in which several preferredembodiments of the invention are shown. This invention may, however, beembodied in many different forms and should not be construed as beinglimited to the embodiments set forth herein. Rather, the embodiments areprovided so that this disclosure is thorough and complete, and fullyconveys the scope of the invention to those skilled in the art.

Referring now to FIGS. 1–3, a section of an erosion control blanket 100constructed in accordance with the principles of the present inventionis set forth and described. Note that each of the drawings have beennumbered with like numbers corresponding to like parts. As best seen inFIG. 2, the erosion control blanket 100 is formed of three layers ofmaterial. The first layer is a top sheet 120 of an open-meshed materialof natural or synthetic fibers. The second layer is of a loose fiberfiller 140 which is arranged to form a three-dimensional matrix andprovides the erosion control blanket with a required amount of loft orresiliency. The third layer is a bottom sheet 160 or open-meshedmaterial which generally resembles the top sheet 120 or first layer inconstruction.

Referring now to FIG. 1, the top sheet 120 is seen to have a open-meshedmaterial or netting with a high percentage of open area. In oneembodiment of the present invention, the openings 130 in this nettingmaterial are rectangular in shape with sides ranging form about 0.50inches to about 1.00 inches in length. The netting itself may be formedof either natural or synthetic materials, and in one preferredembodiment, is of polyethylene (PE), polypropylene (PP), or othersuitable polyolefin. It is particularly desirable to make the top sheet120 or netting of a synthetic material which is both lightweight,strong, and durable enough to resist tearing or rupture of the soilerosion control blanket 100. The netting material may also includevarious additives, as known in the art, to improve resistance toultraviolet (UV) radiation or to impart a particular color. By way ofexample only, a small amount of carbon black additive, about 0.1% toabout 2.5% by weight, may be incorporated into a suitable polymer toimpart both a black color and a significant amount of UV resistance intothe netting material.

Although not shown in FIG. 1, the bottom sheet 160 or netting of theerosion control blanket 100 in accordance with the present invention issubstantially similar in construction to the top sheet 120 as shown anddescribed. That is, the bottom sheet 160 will also have an open-meshedmaterial with a high degree of open area and be made of very similarmaterials to that of the top sheet 120.

Still referring to FIGS. 1–3, in another embodiment of the presentinvention, the top sheet 120 and the bottom sheet 160 may be constructedof polymer materials having slightly different mechanical properties.For example, as the top sheet 120 will be exposed to more directsunlight and UV radiation than the bottom sheet, it may be desirable touse a top sheet 120 which is stronger and heavier than the bottom sheet160. In one preferred embodiment, the top sheet 120 is formed of 600denier, high-tensile, polypropylene material and has a weight of about10.0 pounds/1000 square feet and a strand count of about 9.0 and about13.0 strands/10 inches in the machine and transverse directions,respectively. The netting has rectangular openings with sides of about0.75 inches to about 1.00 inches in length. The top sheet 120 has abreak load of about 57.0 pounds/3 inches in the machine direction andabout 73.0 pounds/3 inches in the transverse direction. However, in thisparticular embodiment, the bottom sheet 160 is formed of 600 denier,high-tensile, polypropylene material and has a weight of about 2.87pounds/1000 square feet and a strand count of about 13.0 to about 14.0strands/10 inches in both the machine and transverse directions. Thenetting has rectangular openings with sides of about 0.70 inches toabout 0.80 inches in length. The bottom sheet 160 has a break load ofabout 29.0 pounds/3 inches in the machine direction and about 23.4pounds/3 inches in the transverse direction.

The filler material 140 of the erosion control blanket 100 of thepresent invention is an arrangement of crimped polymer fibers 150 tocreate a three-dimensional matrix having a desired amount of loft andresiliency. Although the polymer fibers 150 may be arranged in variousways, a randomly dispersed loose fiber fill will generally produce ablanket with sufficient loft. In one embodiment of the presentinvention, the polymer fibers 150 are formed of a post-consumerpolyester, namely polyethylene terephthalate (PET). This particularmaterial is commonly used to form soda bottles and other translucentpackaging containers, and is readily available in post-consumer form. Byway of example only, it is also possible to purchase post-consumer PETwhich is of a particular color, namely green, which is derived fromSPRITE, 7-UP, and other citrus flavored soda bottles. The green-colored,post-consumer PET material is desirable in some applications as itprovides the resulting erosion control blanket with a visuallyattractive green color which tends to blend in with grass and plants.

This post-consumer polyester resin may be recycled into fibers 150 toform the filler material 140 of the blanket 100 according to the presentinvention. These PET fibers 150 offer a high degree of loft when crimpedand tend to be more resilient than other synthetic fibers. In accordancewith the present invention, the PET fibers will have a denier size ofabout 15 to about 500. It is the inventors belief that the post-consumerPET fibers used in the filler of the erosion control blanket of thepresent invention are unique in that this particular fiber has aparticularly good shape memory. That is, that when a blanket 100 filledwith crimped PET fiber materials is compressed and the load issubsequently removed, the crimped fibers 150 and consequently theblanket 100 will tend to spring back to its nearly all of its originaldimension. Additionally, the crimped fibers 150 will tend to entangleand cling one-to-another more aggressively than uncrimped fibers do.This particular feature of crimped fibers serves to reduce the migrationof fibers out of the blanket and further assures consistent blanket loftwith the passage of time. Thus, it is possible to create a erosioncontrol blanket 100 which has a higher degree of loft and is far moreresilient than prior art loose fiber filler erosion control blankets.

The recycled polyester fibers 150 used as filler material in the erosioncontrol blanket 100 of the present invention possess a uniquecombination of mechanical properties. It is notable that thepost-consumer PET fibers have a specific gravity greater than 1.0, anddo not float in water. However, many other synthetic fibers such aspolyethylene, polypropylene and the like have specific gravities of lessthan 1.0 and will tend to float in water. This is a particularly usefulcharacteristic of the post-consumer PET fibers in that erosion controlblankets made in accordance with the present invention may be utilizedin high water runoff areas including water drainage channels.Accordingly, it is easier to keep an erosion control blanket in contactwith the ground when the fibers which fill the blanket do not floatunder hydraulic conditions. If an erosion control blanket tends tofloat, it will be much less effective at reducing soil loss andpreventing the washing away of grass seed and other plant matter whichis intended to grow through the erosion control blanket. The fibermaterial may also include various additives, as known in the art, toimprove resistance to ultraviolet (UV) radiation or to impart aparticular color.

In one embodiment, the post-consumer PET fibers will have denier size ofabout 15 to about 500, and have a preferred denier size of about 350 toabout 450. The post-consumer PET fibers are then crimped using astuffer-box crimper, not shown, as known in the art. In operation, thestuffer-box crimper receives a large number of semi-molten polymerfibers between a pair of smooth metal nip rolls and forces the fibersinto a box or container having fixed dimensions and a variableresistance flapper device on the output opening. It is possible toincrease the number of crimps per inch in the fibers by increasing theresistance of the flapper device of the output from the stuffer box. Inshort, greater resistance on the flapper device results in a highernumber of crimps per inch on the fibers coming out of the stuffer-box.The post-consumer PET fiber 150 used in the present invention willnormally have crimping in a range of about 1.0 to about 3.0 crimps perinch, with a value of 2.0 crimps per inch being preferred. The crimpedPET fibers 150 are cut to lengths ranging from about 5.75 inches toabout 6.25 inches, with a length of about 6.0 inches being preferred.

The post-consumer PET fibers 150 used in the present invention have beentested for resistance to compression. The testing procedure begins byfirst carding an 8.0 to 10.0 gram sample of fibers which are of 2.5inches maximum length. The carded fibers are then weighed out into a3.00±0.05 gram sample using an analytical balance. The 3.0 gram cardedsample is then placed into the 3.0 inch diameter compression cup of anInstron resistance to compression tester. The compression cup is thensealed and air pressure applied to the fiber sample. The testingapparatus then computes a resistance to compression for the fiber samplein pounds. The crimped, post-consumer PET fibers used as a fillermaterial in the present invention exhibited resistance to compressionvalues ranging from about 4.5 pounds to about 6.0 pounds, with anaverage value of about 5.2 pounds. This value may also be converted intoa resistance to compression value expressed pounds per square inch (psi)per gram of fiber. Thus, for a fiber sample with an average resistanceto compression value of about 5.2 pounds, it is possible to calculate avalue of about 0.245 psi/gram of fiber.

An additional measure of crimped PET fiber resiliency may be obtained bystudying the ability of an amount of filler material to recover itsoriginal thickness after the application and removal of a particularload. In one such test, one (1.0) pound of crimped PET fiber loosefiller is placed in a circular container having a 6.0 inch diameter andits thickness is measured. A compressive load of 0.5 psi is then appliedevenly across the top surface of the loose filler for a period of 5.0minutes. After the compressive load is removed, the thickness of theloose filler is measured again. A percent recovery is then computed bydividing the thickness after compression by the original thickness andmultiplying by 100%. For the crimped, post-consumer PET fibers used as afiller material in the present invention, it was determined that theloose filler had a percent recovery value ranging from about 95% toabout 97% of its original thickness.

Referring now to FIG. 4, a block diagram illustrates, by way of exampleonly, the various steps of a manufacturing process 400 which may befollowed to construct an erosion control blanket in accordance with thepresent invention. In one embodiment, post-consumer plastic materialssuch as soda bottles and containers are collected and sorted 405according to polymer types (e.g., polystyrene, polyethyleneterephthalate, polybutylene terephthalate, polyethylene, polypropylene,and so forth). These containers are then mechanically shredded 410 andcleaned 415 with high temperature steam to produce post-consumer scrappolymer which is suitable for reprocessing. A fiber manufacturer maythen purchase scrap polymer of a particular type, such as PET, pelletize420 the scrap polymer, melt the polymer 425 in an extruder, and meltspin 430 fibers from the polymer. These fibers may then be crimped 435using a stuffer-box crimper as described hereinabove and cut 440 to aparticular length to produce a crimped loose fiber filler material. Anerosion control blanket may then be produced by providing top and bottomsheets of netting material 445, randomly dispersing 450 the cut, crimpedpolymer fibers between the top and the bottom sheet, and then stitching455 the top and bottom sheets together. Once the top and bottom sheetsare fastened or stitched together and the loose fiber fill material issecured, it is possible to roll the generally rectangular blankets upinto smaller, cylindrical bundles for shipping and handling.

It is thus believed that the operation and construction of the presentinvention will be apparent from the foregoing description of thepreferred embodiments. While the erosion control blanket materials,configurations and designs as shown are described as being preferred, itwill be obvious a person of ordinary skill in the art that variouschanges and modifications may be made therein without departing from thespirit and scope of the invention, as defined in the following claims.Therefore, the spirit and the scope of the appended claims should not belimited to the description of the preferred embodiments containedherein.

1. A method of making an erosion control blanket for controlling erosionand blending in with a designated type of surrounding area, said methodcomprising the steps of: providing post-consumer polymer material, thepost-consumer polymer material having a color which tends to blend inwith the designated type of surrounding area; cleaning said postconsumer polymer material; forming the cleaned post-consumer polymermaterial into polymer fibers; crimping the polymer fibers at intervalsalong their length to form crimped polymer fibers; cutting the crimpedpolymer fibers to form a loose fiber filler; providing top and bottomsheet netting adapted for receiving said loose fiber fillertherebetween, the top sheet netting comprised of a material having acolor which tends to blend in with the designated type of surroundingarea; and securing the loose fiber filler between said top and bottomsheet netting to form said erosion control blanket having a color whichtends to blend in with the designated type of surrounding area.
 2. Themethod of claim 1, wherein said post-consumer polymer material is apolyester.
 3. The method of claim 2, wherein said polyester ispolyethylene terephthalate.
 4. The method of claim 3, wherein saidpolyethylene terephthalate is substantially of green soda bottlematerial.
 5. The method of claim 1, wherein the crimping step is carriedout using a stuffer-box crimper.
 6. The method of claim 1, wherein thefibers are crimped with about 1.0 to about 3.0 crimps per inch.
 7. Themethod of claim 1, wherein the fibers are cut at a length of about 5.75inches to about 6.25 inches.
 8. The method of claim 1, wherein the stepof forming the cleaned post-consumer polymer material into polymerfibers further comprises the steps of: pelletizing said cleanedpost-consumer polymer material to form polymer pellets; extruding saidpolymer pellets as a polymer melt; and melt spinning said polymer meltto form polymer fibers.
 9. An erosion control blanket constructedaccording to the method of claim 1.